1. Field of the Invention
The present invention generally relates to an apparatus for performing a control, and more particularly relates to an apparatus for performing an electronic control with a fail-safe faculty. The present invention also relates to a control apparatus for controlling the operation of an engine and an automatic transmission device of an automotive vehicle, and more particularly, the present invention pertains to an electronic control apparatus for effectively reducing a so-called racing select shock which occurs upon starting the automotive vehicle with an automatic transmission in a racing state.
2. Related Art Statement
In an automotive vehicle incorporating an engine, an automatic transmission, and a control apparatus including a plurality of sensors, control circuits and actuators, it has been a common practice to achieve the fail-safe faculty by providing specially selected sensors in a multiplex manner, e.g. in a duplex manner, said sensors being important for performing a desired control. For instance, in a control apparatus for controlling a driving power of an automotive vehicle including electronically controlled engine and automatic transmission, sensors for detecting the vehicle running speed are arranged in a duplex manner and output signals of these vehicle running speed sensors are supplied to a computer for controlling the automatic transmission. Even if one of the vehicle running speed sensors becomes out of order, the control for the automatic transmission can still be performed correctly by using an output signal generated by the other vehicle running speed sensor which still operates normally.
It should be noted that in the automatic transmission having a torque converter and a speed change gear mechanism, the shift of the gear position in the speed change gear mechanism is effected in accordance with the running speed V of the vehicle and an engine throttle opening T.sub.H, so that the vehicle running speed sensor is a key sensor. In a control apparatus for the electronically controlled engine, if the vehicle running speed sensor does not work normally, an idling speed of the engine is increased, but this does not seriously affect the running of the engine.
When the sensors are arranged in a multiplex manner, although the fail-safe faculty can be attained, the numbers of I/O ports of CPU, waveform shaping circuits, signal processing programs, abnormal processing programs and so on are increased by the number of sensors which are arranged in a multiplex manner. This results in the construction of the control apparatus and the processing programs becoming complex and the cost potentially being increased.
The above mentioned drawbacks may be reduced by connecting sensors in a multiplex manner for a given control circuit and connecting no sensor to the other control circuit and having a signal generated by the sensor supplied to the other control circuit via a communication line. In this case, the multiplex construction may be attained without increasing the number of sensors. However, in such a control apparatus, if the communication line becomes out of order, a given control could no more be carried out correctly in the other control circuit even if the sensors work normally. This might result in a serious problem.
In the automotive vehicle having the automatic transmission installed therein, when a select operation is effected from a stationary state (N- or P-range) into a running state (D- or R-range), there is produced a select shock upon the engagement of a driving clutch. Particularly, in the case of the racing selection, i.e. when a running range is selected while an accelerator pedal is stepped on in the stationary state, there occurs a very large shock called the racing select shock which causes a driver and passengers to feel uncomfortable.
There have been proposed various methods for mitigating the above mentioned racing select shock. In Japanese Patent Application Laid-open Publications Kokai Sho 61-135,944, 62-292,534 and 60-4,433, there is disclosed a method of reducing the racing select shock by decreasing the engine output before the engagement of the driving clutch, so that an amount of energy absorbed by the driving clutch is decreased.
In Japanese Patent Application Laid-open Publications Kokai Sho 62-17,130 and 63-173,337, there is described another known method of reducing the racing select shock, in which not only the above mentioned reduction in the engine output, but also the reduction in the transfer torque capacity of the clutch are performed. This method can reduce the racing select shock much more effectively as compared with the above mentioned known method.
In the above explained methods of reducing the racing select shock, when a system failure in which one of the controlling elements constituting the control apparatus becomes out of order for instance, when one of the actuators, one of the sensors or the communication faculty does not work satisfactorily, one of the above mentioned three controls, i.e. the reduction in the engine output, the reduction in the transfer torque capacity of the clutch and the shift of the gear position can not be performed and the output torque of the automatic transmission could not be decreased by a desired amount. The inventors have proposed to provide a failure alarm alarming device which is initiated upon system failure, but this solution could not reduce the racing select shock positively.
The above mentioned drawbacks are inherent not only to the control apparatus for the electronically controlled engine and automatic transmission of the automotive vehicle, but also occurs in various other subjects to be controlled.